1. Field of the Invention
The present invention relates to a piping structure of fuel injection pipes applied to a diesel engine and the like. More particularly, the invention relates to a piping structure of fuel injection pipes for an engine having such advantages that irregularities in the amount of fuel injection are reduced to enhance engine performance, or productivity and reliability of the piping structure can be enhanced.
2. Description of the Related Art
Japanese Patent No. 2797745 (patent document 1) can be given as one example of known arts with respect to a fuel injection device of an internal combustion engine.
FIG. 7 is a plan view of the fuel injection device disclosed in the patent document 1. A diesel engine shown in FIG. 7 includes six cylinders, and each of fuel injectors (injection valves) 1a to 1f is provided with each of the cylinders. Each of the fuel injectors 1a to 1f is connected to a fuel accumulator 22 via injection pipes 21a to 21f respectively corresponding thereto. The fuel accumulator 22 is formed in a common rail 53 which extends linearly. Fuel exits 22a to 22f are provided in the fuel accumulator 22 in the common rail 53.
A fuel pump 2 is connected to the fuel accumulator 22 in the common rail 53. The fuel pump 2 comprises two pumps, i.e., a first fuel pump 2a and a second fuel pump 2b. The first and second fuel pumps 2a and 2b are connected to the fuel accumulator 22 via fuel supply pipes 37a and 37b, respectively corresponding thereto. Fuel is alternately discharged from the first and second fuel pumps 2a and 2b. 
In this fuel injection device, as is apparent in FIG. 7, the fuel injectors 1a to 1f are sequentially, from one end to the other, connected to the fuel exits 22a to 22f via the injection pipes 21a to 21f, respectively corresponding thereto. That is, the fuel injector 1a is connected to the fuel exit 22a through the injection pipe 21a, and likewise, the valves, exits and pipes are connected in the following manner: the fuel injector 1bthe injection pipe 21bthe fuel exit 22b, . . . , the fuel injector 1fthe injection pipe 21fthe fuel exit 22f. 
In the example shown in FIG. 7, a fuel introducing position (connecting portion for the fuel supply pipes 37a and 37b) for the fuel accumulator 22 is set between the fuel exits 22b and 22c, the fuel exits 22a to 22f are pitched irregularly, and distance between each of the fuel injectors la to if and each of the fuel exits 22a to 22f is made shorter to thereby allow each of the injection pipes 21a to 21f to have the same length. By allowing each of the injection pipes 21a to 21f to have the same length, the irregularities in the amount of fuel injection are reduced to a low level.
However, with the configuration of the patent document 1 as described above, since the fuel introducing position for the fuel accumulator 22 is set between the fuel exits 22b and 22c, the fuel supply pipes 37 and 37b become long as compared with a case in which, for example, the fuel introducing position is set at an end of the fuel accumulator 22 (a lower section in FIG. 7), and therefore, there is a possibility that reliability is lowered.
Further, with the configuration of the patent document 1, it is necessary to set the positions of the fuel exits 22a to 22f of the fuel accumulator 22 in accordance with cylinder pitches of the engine and thus, the common rail 53 becomes a specified part for each series of engines. Therefore, some kinds of common rails must be prepared in accordance with shapes and types of the engines, which results in the deterioration of productivity and the increase of production cost.